How to Make a Simplified Water Rocket

Introduction: How to Make a Simplified Water Rocket

About: I'm an Electronic Engineer and I have build some small robots and microcontroller based systems. I started with 14 years old controlling an arm with the parallel port of a Spectrum. I studied microprocessor...
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Would you like to be an astronaut?

You can start now creating your own rocket with materials from home or the corner DiY shop.

Step 1: 1. Pressure Insertion End

From the car/mountain bike tire get the valve, clean it and fix to one end of the garden hose.

Be sure it's fixed and with no pressure leaks using epoxy glue.

Step 2: 2. Prepare the Rocket Nozzle

Fit the bottle tap to the Gardena tap nut adaptor. Use epoxy to be sure it's firmly fixed and there is not pressure leaks. I didn't check it and I had to solve it later (see the video attached)

Step 3: 3. the Rocket Nose

To avoid any damage to people or things it's important to attach a soft nose to the front of the rocket:

Cut the tennis ball on two halves.

attach one half to the base of the bottle that serves as top.

Tip: don't use a single glue but several spots spaced 3-4 millimeters (see picture attached). On this way you allow the bottle expansion with the air pressure.

Step 4: 4. the Fins

The fins help the rocket to follow a straight line when flying.

You can make them from rigid plastic plates or with thin ones but reinforced with cardboard and tape as I did:

Prepare three rectangles bigger than the fins you want.

Measure the fin shape with the end shape of the bottle as shown in the picture.

then cut the fins.

Finally attach the fins near the nozzle with hot glue placed at 120 degrees of distance each and as straight as possible to the bottle body.

Step 5: 5. the Launchpad

The launch pad holds the rocket in place, helps to pressurize it and releases it when you want:

Prepare the base and put some wood parts to hold the Gardena standard coupling.

You can use a wood plate that has the hole for the coupling or two halves as I did.

Then fix the coupling with hot glue and leave two holes at the side of the wood plate holder, so the nylon cords can pass through.

fix the nylon cords to the Gardena standard coupling, passing the cords though the holders at the bottom so you can fire the rocket from a distance.

Depending on the rocket you can fix the nozzle to the bottle.

You can see the video with the first tests.

I suggest you to test first the rocket with only air at 1 or 2 bar. Then you can put more pressure and finally use water to give it a boost. Usually 1/3 of the bottle with water is the right amount. If you put more water it will be to heavy to flight very much. Put less than 1/3 and probably you won't optimize the pressure, as water ejection gives more boost than just air.